If Opera crashed, then it probably didn't get to save the cookies that indicate you were logged in. Why is it crashing? You don't really need to have that many browsers open at the same time, do you? You could at least make sure you log in then quit while still logged in.

The OS limits Opera's access to system resources. This causes Opera to choke then crash. The problem is with Firefox, which eats all the RAM.

I do need to have multiple browsers open simultaneously. Firefox has better website (code) inspector tools than either Opera or Chrome and I use a password manager in Firefox that I can't port to Opera. I have so several hundred login credentials stored. Using more than one browser means I'm able to properly test websites and allows me to be more productive (different browsers, different tasks).

Though there is an Opera version of Autofill Forms it is a rebuilt version that uses a different code base and is functionally useless + the new version lacks import compatibility with the old version.

Would be nice if I could start Firefox then close it when not needed, which I can but it sometimes crashes the system before I get chance to close it.

The crashes happen after several hours of uptime, 24 to 48 for example, so Opera has plenty of time to store the cookies.

I'm not worried about the crashes. I'm bothered that Opera fails to fully restore my user session on restart.

In case other web developers arrive here in search of an answer to localhost invalid SSL certs causing Opera to require re-login after browser restart, the solution is to visit opera://flags/#allow-insecure-localhost to enable the Allow Insecure Loclhost setting then relaunch the browser.